The field includes an inflatable underbody convective warming blanket adapted to be deployed under a person for warming the person during clinical procedures such as surgery. More particularly, the underbody blanket may include a bypass duct in communication with interior space in the underbody device. More particularly still, an underbody convective warming blanket may have a structure including an elongate columnar midsection which transitions at an end, or at each end, to a plinth-like configuration.
Warming a person during surgery affords clinical benefits, such as prevention or treatment of hypothermia, encouragement of immune system function, promotion of wound healing, reduction of infection rates, and mitigation of discomfort. An inflatable blanket laid over a person's body is used to warm the person perioperatively. Such a blanket, when inflated with heated air, warms the person principally by convection of warmed air through a permeable portion of the blanket, although conduction and radiation of heat from the blanket also contribute to warming.
However, covering a person for warming may interfere with a variety of surgical procedures by preventing or limiting access to the person. For example, during cardiac surgery access to the thorax, groin and extremities is necessary when blood vessels must be harvested from the legs and arms for bypass construction on the heart. Covering a person with a convective warming blanket may interfere with, if not prevent, the necessary access. Adapting the blanket to avoid interference by reducing its size may compromise its capacity to warm the person. Adapting the blanket to provide access by separable seals may extend and complicate the surgery due to need to integrate the operation and management of the blanket with surgical protocols.
One way to achieve the benefits of warming a person during clinical procedures while providing unobstructed access to the person is to deploy an inflatable underbody convective warming blanket (“underbody blanket”) beneath the person. The person is laid on the underbody blanket which warms the person by convection of warmed air, and also by conduction and radiation, without covering the person. Examples of underbody blankets include an inflatable convective pad described in the assignee's '992 application, the inflatable pad described in the assignee's U.S. Pat. No. 6,102,936, and the assignee's underbody series blankets illustrated and described at www.arizanthealthcare.com.
Underbody blanket and warming blanket constructions differ in significant ways. In this regard, merely rotating a warming blanket to dispose it beneath a person, with the permeable surface supporting the person, and then inflating the device with warmed air provided through an inlet port may not achieve desired warming, for a number of reasons.
A preferred warming blanket construction includes permeable and impermeable sheets that are sealed together at their peripheries to form an interior space between the sheets. Patterns of interior seals between the sheets within the peripheral seal form air distribution structures in the interior space that are intended to maintain a uniform temperature within the warming blanket with a minimal loss of heat. One or more inlet ports are provided in the construction to admit warmed air into the interior space. The warmed air pressurizes and inflates the blanket, and the inflation pressure forces warmed air through the permeable sheet which faces the person when the blanket covers the person. The inlet ports are typically provided in the impermeable sheet, within the peripheral seal.
Warming blankets are not constructed to be used as underbody devices. Rotation of the warming blanket such that the blanket is underneath the person places the impermeable sheet and the inlet port against a supporting surface such as a surgical table, which makes it difficult to couple an air hose to the port. Further, the pressure of the person's body against the inlet port can impede or, in some cases, pinch off the air distribution structures and thereby block distribution of warmed air in the warming blanket. Thus, the supporting device must be modified to accommodate an air hose, and/or the warming blanket must be placed so as to locate the inlet port beyond the periphery of the supporting device.
Moreover, the air distribution structure of a preferred warming blanket construction includes parallel sequences of elongated or closely spaced interior seals arranged to define generally parallel, longitudinal tubular structures when the blanket is inflated. Air enters the warming blanket though a central tube from which it flows laterally through small openings to the other tubes. If placed underneath a patient, the central tube can be pinched off by the person's weight during operation, which will prevent the distribution of warmed air in the warming blanket.
The underbody blanket construction illustrated in US 2006/0052851 accommodates and complements the positioning of a patient directly on the permeable surface. The inlet ports are located at or near sides or edges of the inflatable structure. This construction has no central tube from which pressurized air flows laterally. Instead, relatively short, widely spaced interior seals or stake points define an air distribution structure with a cross hatch of intersecting air passages with major longitudinal and transverse components. However, the underbody blanket is compliant, without significant structure when receiving a flow of warmed, pressurized air, so that the weight of the patient on the permeable surface compresses the underbody blanket. This occludes airflow and prevents heat from reaching the patient's potentially ischemic pressure points, so as to reduce the potential for nosicomial pressure sores and thermal injuries.
Nevertheless, the underbody blanket maintains convective warming of as much of the patient's body as possible, even when the size and weight of the patient occludes airflow through its central portion. In this regard, as seen in FIG. 4 of US 2006/0052851, the underbody blanket construction is generously dimensioned in length and width so as to circulate air along a portion of the air distribution structure positioned inside of the blanket's periphery, around the outside periphery of a patient's body, when the patient lies upon the blanket. This configuration maintains at least a minimal condition of inflation and operation so that the patient is convectively warmed by pressurized air from the air distribution portion at the blanket's periphery.
However, operation of the underbody blanket during certain clinical procedures may be impaired by pinch-off caused by the patient's position. For example, in FIG. 8 of US 2006/0052851, the patient is lying on his side with arms extended and the blanket's periphery sandwiched therebetween. This occludes airflow along the one side of the blanket and increases the airflow path length to parts of the blanket that would otherwise be served by a short path through the occluded section. The width of the middle section of the underbody blanket also makes the peripheral portion of the air distribution structure vulnerable to being pinched off by clinical personnel leaning against a side of the blanket, as when a surgeon braces against a surgical table to lean over a patient when accessing a surgical site. Pinch-off may interrupt some or all of the air flow through the underbody blanket, thereby reducing its therapeutic effect.
Thus, in some applications it is desirable to provide a separate air flow channel to bypass a pinch-off location in an underbody blanket in order to maintain short air flow paths within the interior space of the underbody blanket.
Furthermore, in other applications, it is desirable to narrow the midsection of the underbody blanket in order to reduce the risk of occlusion of the peripheral air flow structure of the underbody blanket.